1. Field of the Invention
The present invention generally relates to an acquisition assist information managing system. More specifically, the present invention relates to an acquisition assist information managing system, an acquisition assist information managing device, and an acquisition assist information managing method, each provided with user equipment and an acquisition assist information providing server. The user equipment performs positioning by acquiring a satellite link with the use of acquisition assist information, and then receives the satellite radio waves from the acquired satellite. The acquisition assist information providing server provides the acquisition assist information. Assist information is information to assist the acquisition of a satellite that outputs satellite radio waves and includes plural items of information.
2. Background Information
Recently, developments have been under way for electronic equipment, such as a mobile phone, to be compliant with so-called 3GPP (Third Generation Partnership Project) standards. The previously present network assist type GPS (Global Positioning System) is adopted for these so-called 3GPP (Third Generation Partnership Project) standards as well. The network assist type GPS positioning system schematically includes mobile user equipment, a computer in a radio network control, and an assist data providing server installed in a satellite access station. The user equipment, computer in the radio network control, and assist data providing server are interconnected to each other via a base station and a network.
The user equipment is configured to perform positioning, for example, by means of a GPS (Global Positioning System). The user equipment acquires a satellite with the use of assist data prior to actual positioning. The radio network control accepts a request for assist data from the user equipment and then makes a request for the assist data to the assist data providing server.
Meanwhile, the assist data providing server manages assist data used to assist the acquisition of a satellite link (hereinafter acquisition of or acquiring a satellite), and it is configured to provide the user equipment with the assist data by way of the radio network control in response to the request from the user equipment. The assist data are acquisition assist information to assist the user equipment when performing positioning as described above by making it easier to acquire a satellite, and they include at least one item of information.
Conventionally, respective items of information in the assist data are selected, for example, by the assist data providing server at the end to provide the assist data. To be more specific, examples of respective items of information in the assist data include the time, the initial location, the ephemeris, the almanac, an ionospheric correction value, and a DGPS correction value.
As has been described, the user equipment in the related art first makes a request for assist data to the assist data providing server, and obtains the assist data from the assist data providing server as has been described prior to the acquisition of the satellite. The assist data include at least one item of information as has been described, and the user equipment is configured to acquire the satellite with the use of all the items of information included in the obtained assist data. For example, when two cases of acquiring four satellites are concerned, it is typical for the user equipment that an acquisition time to acquire four satellites becomes shorter by obtaining assist data that include more kinds of items of information, while the data size of the assist data itself becomes larger as the kinds of items of information included in the assist data are increased.
Incidentally, in general, numerical targets related to the positioning that each operator desires, such as the positioning accuracy and the positioning time, are different from user equipment to user equipment. For example, when positioning is performed simply with the use of the user equipment, it is preferable for the operator that a time needed to complete the positioning is shorter even though the positioning is less accurate. A time needed to complete the positioning referred to herein includes an acquisition time of a satellite, and a positioning time, which is a time needed for actual positioning. Meanwhile, for example, when positioning is performed in detail with the use of the user equipment, a higher degree of positioning accuracy is desired even when it takes longer to complete the positioning.
When the operator wishes to perform positioning using the user equipment in the related art, for example, a system has been disclosed in which positioning is performed for the desired positioning accuracy or within a desired positioning time, by switching positioning modes per se, such as a base station information using mode to perform positioning with the use of information of the base station, and a so-called stand-alone GPS positioning mode, as shown in Japanese Patent Publication JP-A-2002-196063, which is hereby incorporated by reference.
The user equipment in the related art that changes the positioning modes, however, needs time for a switching judging process to switch the positioning modes prior to actual positioning. Hence, the user equipment in the related art cannot shorten the time needed to complete the positioning including such a switching judging process, which makes it difficult to configure the user equipment to reach a desired numerical target related to positioning.
Meanwhile, the user equipment in the related art that does not change the positioning modes acquires a satellite using items of information that are not essentially necessary but included in the assist data obtained from the assist data providing server. This raises a problem in that the positioning is not performed in a way to reach the numerical target related to positioning that the operator of the user equipment desires, such as the time, including the acquisition time, needed to complete the positioning and the positioning accuracy.
To be more specific, for example, when it is sufficient to acquire a satellite at a high speed and the positioning accuracy is not required as has been described, there is no need to use assist data including items of information that can increase the positioning accuracy. This is because of the fact that the items of information in the assist data do not match with the acquisition time or the positioning accuracy that the operator of the user equipment desires.
It may seem possible to acquire a satellite by selecting parts of items of information instead of acquiring a satellite with the use of all the items of information included in the assist data. This alternative, however, is infeasible because processing time becomes too long when the processing ability of the user equipment is considered.
Hence, the user equipment in the related art has a problem in that when it performs positioning by acquiring a satellite with the use of all the items of information in the assist data obtained from the assist data providing server, it fails to perform the positioning within a desired time, including an acquisition time, needed to complete the positioning with the desired positioning accuracy.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved acquisition assist information managing system, acquisition assist information managing device, and acquisition assist information managing method. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.